#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <algorithm>
#include <string.h>
using namespace std;
#define PI atan2(0, -1)
#define epsilon 1e-9
#define INF 5000000000000000000
#define MOD 1000000007
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
int N, arr [10010], maxi [10010];
long long M = 1000007, dp [2][10010], saves [10010], ret = 1;
int main(){
//freopen("sort.in", "r", stdin); freopen("sort.out", "w", stdout);
ios_base::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(10);
cin >> N; fill(dp[0], dp[0]+N+1, 1); saves[0] = 1;
for(int i = 0; i < N; i++){
cin >> arr[i];
maxi[i+1] = max(maxi[i], arr[i]);
}
for(int i = 1; i < N; i++){
int curr = i%2, prevy = curr^1;
for(int j = 0; j <= N; j++) dp[curr][j] = (j*dp[prevy][j]+dp[prevy][j+1])%M;
saves[i] = dp[curr][maxi[N-1-i]];
}
for(int i = 0; i < N; i++) ret = (ret+(arr[i]-1)*saves[N-1-i])%M;
cout << ret << '\n';
return 0;
}
/******************************
Kateba ii dake no hanashi darou
Success is only a victory away
- No Game No Life Opening
******************************/
